Magneto optical deflector

Abstract

The invention concerns the magneto-optical deflectors which enable an incident beam of radiant energy to be deflected in a variable manner under the control of a magnetic field. It consists in using a thin film of a magnetic material forming a diffraction grating, means for travelling the incident beam along the plane of this thin film, and means for magnetically controlling the step-width of the grating, thus controlling the angle of deflection given by this grating.

What we claim is: 
     
       1. A magneto-optical deflector for deflecting an incident light beam having a first direction into at least one emerging beam having a deflected direction slightly variable about a fixed second direction, which comprises: a thin layer of homogeneous magnetic material having oppositely magnetized stripe domains, said domains extending along a third direction parallel to the layer;   means for applying to said layer a magnetic field parallel to said third direction; the spacing of the domains being dependent upon the value of said field; and   means for entering said incident beam into said layer, and means for extracting said emerging beam from the layer.   
     
     
       2. A deflector as claimed in claim 1, wherein said incident beam is a beam of parallel monochromatic light having a first polarization for initially propagating in said layer according to a first pure mode of guided propagation, and said layer is made with Gadolinium and Gallium substituted garnet of Yttrium and Iron; said emerging beam having a second polarization crossed with said first polarization and corresponding to a second pure mode of guided propagation induced by said layer. 
     
     
       3. A deflector as claimed in claim 2, wherein said entering means comprise a bi-refractive entry prism for selecting the polarization of said incident beam. 
     
     
       4. A deflector as claimed in claim 3, wherein the composition of said layer is substantially given by the formula Gd 0 .45 Y 2 .55 Fe 4 .2 Ga 0 .8 O 12  ; the layer being deposited onto a substrate made with a Gadolinium and Gallium garnet. 
     
     
       5. A deflector as claimed in claim 4, wherein the thickness of said layer is substantially equal to 4.4 μm. 
     
     
       6. A deflector as claimed in claim 5, wherein said incident beam is an infrared beam having a wavelength substantially equal to 1.15 μm. 
     
     
       7. A deflector as claimed in claim 6, wherein first and second directions are inclined relative to said third direction at angles substantially equal to 1.3°; said angles being measured in the atmosphere outside the layer. 
     
     
       8. A deflector as claimed in claim 3, wherein said extracting means comprise a bi-refractive exit prism for separating from said emerging beam a non deflected beam having said first directions and corresponding to a remainder part of the incident beam being propagated according to said first pure mode. 
     
     
       9. A deflector as claimed in claim 8, further comprising a screen for intercepting said non deflected beam. 
     
     
       10. A deflector as claimed in claim 7, wherein the incident beam propagates into said layer along substantially 1 cm.